GIS-Based Geospatial Assessment of Net Land Surface Change for Identifying Erosion-Accretion Hotspots Along the Padma River in Bangladesh

Abstract

Erosion is a continuous natural process that reshapes Earth’s surface. It causes geohazards, loss of fertile lands, and has detrimental effects on the environment. This study provides an extensive analysis of erosion and accretion patterns over decades along both banks of the Padma River, the main distributary of the Ganges. Satellite images from Landsat and Sentinel were processed in ArcGIS to extract and compare banklines using a 5 km river-reach framework to identify net land surface change and erosion-accretion hotspots. The temporal scope included both long-term decadal analysis from 1990 to 2020 and recent annual assessment from 2016 to 2022; however, the two periods were interpreted as period-specific estimates rather than statistically tested temporal trends. Results show that erosion dominated accretion across both banks. During 1990-2020, average erosion and accretion rates on the left bank were 464 ha/year and 18 ha/year, respectively, while the corresponding rates on the right bank were 758 ha/year and 285 ha/year, respectively. For the recent 2016-2022 period, the average erosion and accretion rates were 221 ha/year and 177 ha/year on the left bank, and 1035 ha/year and 171 ha/year on the right bank, respectively. These values indicate that the right bank experienced higher erosion activity than the left bank in both the long-term and recent assessment periods. Finally, the 5 km chainage-based hotspots analysis using the net land surface change identified the most critical localized erosion-prone reaches on the right bank within Faridpur, Madaripur, and Shariatpur, while major left-bank erosion hotspots were found within Manikganj, Munshiganj, and Dhaka. These results highlight the importance of priority-based erosion monitoring and riverbank management for industrial site selection, riverbank protection planning, and identifying suitable locations for hydraulic structures along the river. ABSTRAK: Hakisan adalah proses semula jadi berterusan yang membentuk semula permukaan bumi serta menyebabkan geobahaya, kehilangan tanah subur, dan kesan buruk terhadap alam sekitar. Kajian ini menganalisis corak hakisan dan akresi di kedua-dua tebing Sungai Padma, iaitu cabang utama Sungai Ganges. Imej satelit Landsat dan Sentinel diproses menggunakan ArcGIS bagi mengekstrak serta membandingkan garis tebing berdasarkan rangka kerja rantaian sungai 5 km bagi mengenal pasti perubahan bersih permukaan tanah dan lokasi tumpuan hakisan-akresi. Skop temporal merangkumi analisis dekad jangka panjang dari 1990 hingga 2020 dan penilaian tahunan terkini dari 2016 hingga 2022; namun, kedua-dua tempoh ini ditafsir sebagai anggaran khusus tempoh dan bukan sebagai trend temporal yang diuji secara statistik. Dapatan menunjukkan bahawa hakisan lebih dominan berbanding akresi di kedua-dua tebing. Bagi tempoh 1990-2020, kadar purata hakisan dan akresi di tebing kiri masing-masing ialah 464 ha/tahun dan 18 ha/tahun, manakala di tebing kanan masing-masing ialah 758 ha/tahun dan 285 ha/tahun. Bagi tempoh 2016-2022, kadar purata hakisan dan akresi ialah 221 ha/tahun dan 177 ha/tahun di tebing kiri, serta 1035 ha/tahun dan 171 ha/tahun di tebing kanan. Nilai ini menunjukkan bahawa tebing kanan mengalami aktiviti hakisan yang lebih tinggi berbanding tebing kiri pada kedua-dua tempoh penilaian. Analisis lokasi tumpuan berasaskan rantaian 5 km mengenal pasti kawasan hakisan kritikal di tebing kanan Faridpur, Madaripur, dan Shariatpur, manakala lokasi utama di tebing kiri dikenal pasti Manikganj, Munshiganj, dan Dhaka. Dapatan ini menekankan kepentingan pemantauan hakisan dan pengurusan tebing sungai secara berkeutamaan bagi pemilihan tapak industri, perancangan perlindungan tebing sungai, dan penentuan lokasi struktur hidraulik di sepanjang sungai.